University of Maryland professor Timothy Summers explains in a Barron’s column why privacy is a thing of the past in modern political campaigns.

The use of information about the lives and concerns of voters is probably as old as democracy. Candidates in the Roman Republic employed nomenclators, who were slaves specially trained to whisper names and facts about voters that their masters could use to charm the voters. Franklin D. Roosevelt’s campaign manager, James A. Farley, kept a “farleyfile” of notecards so his boss could be reminded of names and facts about political contacts Roosevelt might wish to influence.

In the age of computers, political campaigns use information about the lives of voters on a massive scale, and not just to charm but also to manipulate. The momentous success of Barack Obama’s campaigns in 2008 and 2012 demonstrated that data mining and new processing technologies could be used to persuade and target voters in ways previously unfathomable. The winning strategy of that campaign involved capturing and profiling personal data on the U.S. voting public and precisely crafting messages that would resonate with voters from specific constituencies.

In 2012, the New York Times published an article that described how political strategists, regardless of party affiliation, analyzed voter personal data and used subtle psychological cues, rewards, and threats to train voters to vote their way. Campaigns “have examined voters’ online exchanges and social networks to see what they care about and whom they know,” the newspaper said.

Campaign employees confirmed the use of other strategies, including “authorizing tests to see if, say, a phone call from a distant cousin or a new friend would be more likely to prompt the urge to cast a ballot”; planting software cookies on voters’ computers, “to see if they frequent evangelical or erotic Websites, for clues to their moral perspectives”; and shaming nonvoters for their failure to vote if the voters were expected to support a client candidate.

Presidential candidates are invested in the business of spying. Their minions are collecting, storing, and analyzing your personal data. Of course, the campaigns do a great job of ensuring that voters are oblivious to these tactics. As a Republican campaign official said, “You don’t want your analytical efforts to be obvious because voters get creeped out.”